Whole exome sequencing in 17 consanguineous Iranian pedigrees expands the mutational spectrum of inherited retinal dystrophies

Inherited retinal dystrophies (IRDs) constitute one of the most heterogeneous groups of Mendelian human disorders. Using autozygome-guided next-generation sequencing methods in 17 consanguineous pedigrees of Iranian descent with isolated or syndromic IRD, we identified 17 distinct genomic variants in 11 previously-reported disease genes. Consistent with a recessive inheritance pattern, as suggested by pedigrees, variants discovered in our study were exclusively bi-allelic and mostly in a homozygous state (in 15 families out of 17, or 88%). Out of the 17 variants identified, 5 (29%) were never reported before. Interestingly, two mutations (GUCY2D:c.564dup, p.Ala189ArgfsTer130 and TULP1:c.1199G > A, p.Arg400Gln) were also identified in four separate pedigrees (two pedigrees each). In addition to expanding the mutational spectrum of IRDs, our findings confirm that the traditional practice of endogamy in the Iranian population is a prime cause for the appearance of IRDs.